26.5625 Gbaud PAM-4 short-reach transmission at 75°C using 850 nm VCSELs with strategic oxide guiding layer positioning.

This article presents an all-epitaxy approach to reduce the root mean square spectral width (ΔλR M S) of 850 nm oxide-confined vertical cavity surface-emitting lasers (VCSELs) with a large aperture of 7 µm through strategic optimization of the oxide guiding layer within the epitaxy structure. At 75°C, the VCSEL demonstrates a ΔλR M S of ∼0.3 nm at a bias current of 7.5 mA. Furthermore, the VCSEL achieves successful transmission of 26.5625 Gbaud PAM-4 modulation over a short-reach (SR) OM4 fiber link while maintaining a TDECQ budget below the 4.5 dB specified by 50G IEEE Ethernet standards.

Monolithically integrated 940†nm VCSELs on bulk Ge substrates.

This research successfully developed an independent Ge-based VCSEL epitaxy and fabrication technology route, which set the stage for integrating AlGaAs-based semiconductor devices on bulk Ge substrates. This is the second successful Ge-based VCSEL technology reported worldwide and the first Ge-based VCSEL technology with key details disclosed, including Ge substrate specification, transition layer structure and composition, and fabrication process. Compared with the GaAs counterparts, after epitaxy optimization, the Ge-based VCSEL wafer has a 40% lower surface root-mean-square roughness and 72% lower average bow-warp. After device fabrication, the Ge-based VCSEL has a 10% lower threshold current density and 19% higher maximum optical differential efficiency than the GaAs-based VCSEL.

25 Gb/s NRZ transmission at 85°C using a high-speed 940 nm AlGaAs oxide-confined VCSEL grown on a Ge substrate.

In this Letter, we present a comprehensive analysis of the high-speed performance of 940 nm oxide-confined AlGaAs vertical-cavity surface-emitting lasers (VCSELs) grown on Ge substrates. Our demonstration reveals a pronounced superiority of Ge-based VCSELs in terms of thermal stability. The presented Ge-VCSEL has a maximum modulation bandwidth of 16.1 GHz and successfully realizes a 25 Gb/s NRZ transmission at 85 ∘C. The experimental results underscore the significance and potential of Ge-VCSELs for applications requiring robust performance in high-temperature environments, laying the cornerstone for the future development of VCSEL devices.

Presentations of Children with Suspected Sepsis Caused by Acute Infectious Diarrhea in the Pediatric Emergency Department.

BACKGROUND: Acute infectious diarrhea is a common cause of hospitalization in children. Hence, early identification of acute bacterial gastroenteritis with suspected sepsis in pediatric emergency departments (EDs) is important. This study aimed to describe the clinical spectrum and initial characteristics of children who were presented to a pediatric ED with acute infectious diarrhea and suspected sepsis. METHODS: Between April 2020 to March 2021, children with clinical diagnoses of acute bacterial colitis and suspected sepsis who were admitted to the pediatric ED were prospectively enrolled. The following data were obtained and compared between different age groups of children: including demographics, presentation, laboratory tests, culture results, treatment modalities, complications, and short-term outcomes. RESULTS: A total of 105 patients (70 males and 35 females; mean age: 3.75 ± 3.52 years) were enrolled in this study. Of them, 89 (84.8%) patients were <6 years of age, and 80 (76.2%) patients required hospitalization for a duration of 4.7 ± 2.08 days. C-reactive protein (CRP) and procalcitonin (PCT) levels were significantly higher in the admission (both p < 0.001) and anti-biotic treatment groups (both p < 0.001). Salmonella enteritidis was the most common organism cultured from the stool and blood samples (39 of 91 (38.5%) and 2 of 105 (1.9%), respectively). CONCLUSIONS: The primary causative organism of acute infectious diarrhea identified in this study was S. enteritidis. Age and elevated serum CRP or PCT levels could be important factors in the decisions of emergency physicians regarding hospitalization and antibiotic therapies for pediatric acute infectious diarrhea.

Zone-addressable 20 × 20 940 nm VCSEL array with a 5-bit binary number pattern.

This article presents a monolithically zone-addressable 20 × 20 940 nm vertical-cavity surface-emitting laser (VCSEL) array with a binary number pattern design for sensing applications. The emitters in this VCSEL array have a uniquely designed binary pattern design, with each row representing a 5-bit pattern designed to aid pattern-matching algorithms to deduce the shape and depth information efficiently. Approximately 200 VCSELs are arranged in four individually addressable light-emitting zones, with ∼50 emitters in each zone. Each zone generates laser pulses up to 7.2 W in peak power.

Achieving ns-level pulsed operation of up to 6.27 W with a 1.55-µm BH-DFB laser for LiDAR applications.

In this Letter, we present a highly efficient 1.55-µm buried heterostructure distributed feedback (BH-DFB) laser diode. The optimized epitaxial structure resulted in a threshold current of 12 mA and a differential slope efficiency of 0.433 W/A. The laser exhibited stable single longitudinal mode characteristics in both high current injection and broad temperature range testing. Additionally, the ns-level pulsed operation characteristics of the BH-DFB laser were verified, achieving a pulse peak power of 6.27 W with a pulse optical width of 20.4 ns. The watt-level pulse optical power was achieved with a single active region. With its eye-safe wavelength, high operating efficiency, stable single-mode spectral characteristics, and high pulse optical power, the 1.55-µm BH-DFB laser is a promising light source for LiDAR systems.

Evaluation of registered nurses' interprofessional emergency care competence through the gamification of cardiopulmonary resuscitation training: a cross-sectional study.

BACKGROUNDS: Cardiopulmonary resuscitation (CPR) training is generally led by instructors in a classroom; thus, conventional teaching materials used in CPR training are often constrained by spatiotemporal factors, limiting learners' interest and sense of achievement in learning and preventing them from effectively applying what they learn in practice. For greater effectiveness and more flexible application, clinical nursing education has increasingly emphasized contextualization, individualization, and interprofessional learning. This study determined the self-assessed emergency care competencies of nurses who received gamified emergency care training and explored the factors associated with those competencies. METHODS: Quota sampling of nurses working at a certain regional hospital in central Taiwan was conducted, and a structured questionnaire was administered to the recruited nurses. A total of 194 valid responses were collected. The research tool was a scale measuring the participants' emergency care competencies after they received gamified emergency care training. The data were analyzed using descriptive and inferential statistics and multiple regression. RESULTS: Of the recruited participants, 50.52% were ≤ 30 years old; 48.45% worked in the internal medicine department; 54.64% graduated from 2-year university technical programs; 54.12% were N2 registered nurses; 35.57% and 21.13% had ≥ 10 and 1-3 years of work experience, respectively; and 48.45% worked in general wards. User need (r = 0.52, p = 0.000), perceived usefulness (r = 0.54, p = 0.000), perceived ease of use (r = 0.51, p = 0.000), and usage attitude (r = 0.41, p = 0.000) were positively correlated with emergency care competencies. Furthermore, the multiple regression analysis revealed that perceived usefulness was the primary factor associated with the participants' emergency care competencies. CONCLUSIONS: The results of this study may serve as a reference for acute care facility authorities in designing advanced nursing competency standards and emergency care training programs for nurses.

40.1-GHz sub-freezing 850-nm VCSEL: microwave extraction of cavity lifetimes and small-signal equivalent circuit modeling.

We present an 850-nm vertical-cavity surface-emitting laser (VCSEL) constructed for a wide operating temperature range from 25°C to -50°C sub-freezing temperature, demonstrating 40.1-GHz at -50°C. The optical spectra, junction temperature, and microwave equivalent circuit modeling of a sub-freezing 850-nm VCSEL between -50°C and 25°C are also discussed. Reduced optical losses, higher efficiencies, and shorter cavity lifetimes at sub-freezing temperatures are the leading causes of the improved laser output powers and bandwidths. The e-h recombination lifetime and the cavity photon lifetime are shortened to 113 and 4.1 ps, respectively. Could potentially supercharge VCSEL-based sub-freezing optical links for applications in frigid weather, quantum computing, sensing, aerospace, etc.

29 GHz single-mode vertical-cavity surface-emitting lasers passivated by atomic layer deposition.

The fabrication processes of high-speed oxide-confined single-mode (SM)-vertical-cavity surface-emitting lasers (VCSELs) are complex, costly, and often held back by reliability and yield issues, which substantially set back the high-volume processing and mass commercialization of SM-VCSELs in datacom or other applications. In this article, we report the effects of Al2O3 passivation films deposited by atomic layer deposition (ALD) on the mesa sidewalls of high-speed 850-nm SM-VCSELs. The ALD-deposited film alleviates the trapping of carriers by sidewall defects and is an effective way to improve the performance of SM-VCSELs. The ALD-passivated SM-VCSELs showed statistically significant static performance improvements and reached a believed to be record-breaking SM-modulation bandwidth of 29.1 GHz. We also propose an improved microwave small-signal equivalent circuit model for SM-VCSELs that accounts for the losses attributed to the mesa sidewalls. These findings demonstrate that ALD passivation can mitigate processing-induced surface damage, enhance the performance of SM-VCSELs, and enable mass production of high-quality SM-VCSELs for mid- to long-reach optical interconnects.

Coupling angle tolerance of the 850-nm single-mode VCSEL output collimated by lensed OM4-MMF or GI-SMF for a NRZ-OOK link.

By collimating the single-mode (SM) vertical-cavity surface-emitting laser (VCSEL) at 850 nm with either the OM4 multi-mode fiber (OM4-MMF) or the graded-index single-mode fiber (GI-SMF) with lensed end-face, the directly encoded non-return-to-zero on-off keying (NRZ-OOK) data transmission performance is characterized when tilting the coupling angle with respect to the surface normal of the SM-VCSEL. In comparison with the lensed OM4-MMF and lensed SMF coupling, the lensed OM4-MMF collimator shows a large coupling angle tolerance with the coupling efficiency only degraded by 5% when enlarging the tilted angle from 0° to 10°. In contrast, the lensed GI-SMF collimator attenuates the coupled SM-VCSEL output by more than 50% when tilting the coupling angle up to 10°. For the lensed OM4-MMF coupling, the receivable NRZ-OOK data rate in BtB and after 100-m OM4-MMF cases can achieve 50 Gbit/s with its corresponding BER degraded from 6.5 × 10-10 to 8.8 × 10-10 when enlarging its tilting angle ranged from 0° to 10°. By changing the collimator to the lensed SMF, the decoded BER significantly degrades from 5.8 × 10-5 to 1.2 × 10-1 when coupling and transmitting the NRZ-OOK data at 50 Gbit/s. Owing to the low coupling efficiency via the lensed SMF collimator, the error-free NRZ-OOK data rate under the lensed SMF coupling somewhat decreases to 35 Gbit/s in the BtB link and to 32 Gbit/s after the 100-m GI-SMF link with allowable coupling angle tilted from 0° to 4°. This work confirms the applicability of the lensed MMF or SMF collimator for coupling the SM-VCSEL output with a relatively large tolerance on the tilting angle with respect to the surface normal of the SM-VCSEL.

Performance Analyses of Photonic-Crystal Surface-Emitting Laser: Toward High-Speed Optical Communication.

This study conducts comprehensive performance analyses of a commercial photonic-crystal surface-emitting laser (PCSEL) via small-signal measurement and the bit-error-rate test. Meanwhile, the radio frequency characteristics of the PCSEL are unveiled for the first time. Compared to the vertical-cavity surface-emitting lasers, the PCSEL shows great potential for a broader optical bandwidth that is benefited from the high optical-confinement factor. A maximum bandwidth of around 2.32 GHz is experimentally observed when the PCSEL was biased at 340 mA. Moreover, a theoretical calculation was applied to shed light on the characteristics of the small-signal measurement, providing a deep insight into the corresponding intrinsic response model. The signal transmission capability of the PCSEL was investigated as well. The maximum bit rate and corresponding rise time transmitted at 500 Mbps are 1.2 Gbps and 186.16 ps, respectively. Thus, a high-speed PCSEL can be realised with a shrunk form factor, serving as a promising candidate for the next-generation light sources in high-speed optical communication.

Association between Shock Index and Emergency Department Cardiac Arrest.

BACKGROUND: In the emergency department (ED), early identification of patients at risk of cardiac arrest is paramount, especially in the context of overcrowding. The shock index (SI) is defined as the ratio of heart rate to systolic blood pressure. It is a tool used for predicting the prognosis of critically ill and injured patients. In this study, we have discussed the relationship between SI and cardiac arrest in the ED. METHODS: Patients who experienced cardiac arrest in the ED were classified into two groups, SI ≥ 0.9 and < 0.9, according to their triage vital signs. The association between SI ≥ 0.9 and in-hospital mortality was analyzed in five different etiologies of cardiac arrest, including hypoxia, cardiac cause, bleeding, sepsis, and other metabolic problems. RESULTS: In total, 3,313 patients experienced cardiac arrest in the ED. Among them, 1,909 (57.6%) had a SI of ≥0.9. The incidence of SI ≥ 0.9 in the five etiologies was 43.5% (hypoxia), 58.1% (cardiac cause), 56.1% (bleeding), 58.0% (sepsis), and 65.5% (other metabolic problems). SI was associated with in-hospital mortality (adjusted odds ratio (aOR), 1.6; 95% confidence interval (CI), 1.5-1.8). The aOR (CI) in the five etiologies was 1.3 (1.1-1.6) for hypoxia, 1.8 (1.6-2.1) for cardiac cause, 1.3 (0.98-1.7) for bleeding, 1.3 (1.03-1.6) for sepsis, and 1.9 (1.5-2.1) for other metabolic problems. CONCLUSION: More than half of the patients who experienced cardiac arrest in the ED had a SI ≥ 0.9. The SI was also associated with in-hospital mortality after cardiac arrest in the ED. SI maybe used as a screening tool to identify patients at risk of cardiac arrest in the ED and a predictor of mortality in those experiencing cardiac arrest in the ED.

Investigation of Normally-Off p-GaN/AlGaN/GaN HEMTs Using a Self-Terminating Etching Technique with Multi-Finger Architecture Modulation for High Power Application.

Normally-off p-gallium nitride (GaN) high electron mobility transistor (HEMT) devices with multi-finger layout were successfully fabricated by use of a self-terminating etching technique with Cl2/BCl3/SF6-mixed gas plasma. This etching technique features accurate etching depth control and low surface plasma damage. Several devices with different gate widths and number of fingers were fabricated to investigate the effect on output current density. We then realized a high current enhancement-mode p-GaN HEMT device with a total gate width of 60 mm that exhibits a threshold voltage of 2.2 V and high drain current of 6.7 A.

Investigation of the current influence on near-field and far-field beam patterns for an oxide-confined vertical-cavity surface-emitting laser.

This experiment presents dynamic behaviors between the operating current and the optical beam images of vertical-cavity surface-emitting lasers (VCSELs) with two different aperture diameters of 3 µm (single-mode) and 5 µm (multi-mode). These VCSELs exhibit complex optical phenomena under current injection such as thermal effects, modal competition, carrier distribution, and laser coherence which make the light field distribution difficult to predict. In this report, the DC properties, optical spectrum, and optical images were measured together at different operating currents to accurately evaluate the characteristics of the lasers. Unlike previous works, the variations of the far-field angle were precisely evaluated by the side-mode-suppression ratio (SMSR) of the optical spectrum. In addition to commonly used transform functions such as the Gaussian beam formula, the SMSR provides another tool for the judgment of far-field divergence which could prevent inaccurate analysis. Moreover, the impact of thermal lensing was calculated by the DC measurement and demonstrated by the far-field measurement at high injection current. Through this experiment, the interaction between the injection carrier, thermal lens effect, and current spreading was described as fully as possible.

Highly conductive nanometer-thick gold films grown on molybdenum disulfide surfaces for interconnect applications.

Thin gold (Au) films (10 nm) are deposited on different substrates by using a e-beam deposition system. Compared with sapphire and SiO2 surfaces, longer migration length of the Au adatoms is observed on MoS2 surfaces, which helps in the formation of a single-crystal Au film on the MoS2 surface at 200 °C. The results have demonstrated that with the assistance of van der Waals epitaxy growth mode, single-crystal 3D metals can be grown on 2D material surfaces. With the improved crystalline quality and less significant Au grain coalescence on MoS2 surfaces, sheet resistance 2.9 Ω/sq is obtained for the thin 10 nm Au film at 100 °C, which is the lowest value reported in literature. The highly conductive thin metal film is advantageous for the application of backend interconnects for the electronic devices with reduced line widths.

Chirp-free optical-signal generation using dual-and-direct current-voltage modulation of transistor lasers.

Transistor lasers (TLs) can be current-modulated as a diode laser or voltage-modulated as a Franz-Keldysh electro-absorption modulator. These two modulation schemes result in opposite frequency shifts that can cancel each other. In this work, we present the principle of generating optical signals with minimal frequency chirps using TLs. With the proper setting of pulse shapes for the current and voltage inputs, optical signals that are robust against distortions can be directly output from TLs for the medium-distance or long-distance optical fiber communication.

High-speed integrated micro-LED array for visible light communication.

In this Letter, we report high-speed integrated 14 µm in diameter micro-light-emitting diode (µLED) arrays with the parallel configuration, including ${2} \times {2}$2×2, ${2} \times {3}$2×3, ${2} \times {4}$2×4, and ${2} \times {5}$2×5 arrays. The small junction area of µLED (${\sim}{191}\;\unicode{x00B5}{\rm m}^2$∼191µm2) in each element facilitates the operation of higher injection current density up to ${13}\;{{\rm kA/cm}^2}$13kA/cm2, leading to the highest modulation bandwidth of 615 MHz. The optical power of ${2} \times {5}$2×5 array monotonically increases (${\sim}{10}$∼10 times higher) as the number of arrays increases (1 to 10), while retaining the fast modulation bandwidth. A clear eye diagram up to 1 Gbps without any equalizer further shows the capability of this high-speed transmitter for VLC. These results mean that tailoring the optical power of µLEDs in a parallel-biased integrated array can further enhance the data transmission rate without degradation of the modulation bandwidth.

Tungsten Diselenide Top-gate Transistors with Multilayer Antimonene Electrodes: Gate Stacks and Epitaxially Grown 2D Material Heterostructures.

We have demonstrated that with e-beam deposition of a thin Al2O3 layer before atomic layer deposition, a uniform Al2O3 film can be obtained on WSe2/sapphire samples. Device performances are observed for WSe2 top-gate transistors by using oxide stacks as the gate dielectric. By using thermal evaporation, epitaxially grown multilayer antimonene can be prepared on both MoS2 and WSe2 surfaces. With multilayer antimonene as the contact metal, a significant increase in drain currents and ON/OFF ratios is observed for the device, which indicates that high contact resistance between metal/2D material interfaces is a critical issue for 2D devices. The observation of multilayer antimonene grown on different 2D material surfaces has demonstrated less dependence on the substrate lattice constant of the unique van der Waals epitaxy for 2D materials. The results have also demonstrated that stacking 2D materials with different materials plays an important role in the practical applications of 2D devices.

Design, Modeling, and Fabrication of High-Speed VCSEL with Data Rate up to 50 Gb/s.

We have studied the characteristics of frequency response at 850-nm GaAs high-speed vertical-cavity surface-emitting lasers (VCSELs) with different kinds of oxide aperture sizes and cavity length using the PICS3D simulation program. Using 5-µm oxide aperture sizes, the frequency response behavior can be improved from 18.4 GHz and 15.5 GHz to 21.2 GHz and 19 GHz in a maximum of 3 dB at 25 °C and 85 °C, respectively. Numerical simulation results also suggest that the frequency response performances improved from 21.2 GHz and 19 GHz to 30.5 GHz and 24.5 GHz in a maximum of 3 dB at 25 °C and 85 °C due to the reduction of cavity length from 3λ/2 to λ/2. Consequently, the high-speed VCSEL devices were fabricated on a modified structure and exhibited 50-Gb/s data rate at 85 °C.

Pulse compression irrespective of fiber dispersion using chirp of transistor lasers.

The voltage modulation of transistor lasers (TLs) through Franze-Keldysh absorption can impose an unconventional chirp on optical signals. In this Letter, we model this chirp effect and demonstrate how the output Gaussian pulse is reshaped through optical fibers. It is shown that pre-chirped pulses of TLs may be compressed in fibers with both normal and anomalous dispersions.